Magnetic latch



Sept. 19, 1961 R. s. DIDIER 3,001,049

MAGNETIC LATCH Filed Nov. 30, 1959 2 Sheets-Sheet 1 y A 26 21 26 29 2'5 32 al FIG. 2.

INVENTOR.

ROBERT G. DIDIER ATTORNEY p 9, 96 R. G. DIDIER 3,001,049

' MAGNETIC LATCH Filed Nov. 50, 1959 2 Sheets-Sheet 2 INVENTOR.

ROBERT G. DIDIER ATTORN EY Patented Sept. 19, 1961 United States Patent Dec This invention relates to magnetic control devices of the type which include an armature movable in response to magnetomotive force. More particularly, the invention relates to magnetic contact devices of a latching type,

wherein a permanent magnet is provided for normally holding the movable armature in an attracted position, and having means for reducing the magnetic flux to' permit the movable armature to transfer to another position.

The device of this invention assumes either of two positions whereby electrical contacts may be alternately closed and opened to make and break electrical circuits associated therewith. The 'device may include two permanent magnets for alternately retaining andlatching the ends of a movable armature. As either one of such magnets is neutralized by an electromagnetically induced flux, the armature is'released to pivot under the influence of the other permanent magnet. This permits one set of associated contacts to be opened and another set closed. The neutralizing flux need only be applied for a verybrief time in order to permit'the; armature to transfer. This device is operable by alternating current without the use of rectifie'rs or resorting to laminated construction.

Alternatively, a single permanent magnet may be used to provide a simple relay type operation with movement of the armaturein one direction being effected by a pull coil, and movement in the other direction being accomplished by the flux of the permanent magnet upon interruption of the pull or holding circuit current. The

:permanent magnet replaces the conventionally usedreturn spring and its inherent shortcomings.

An object of the present invention is to provide amag- ,netic latching device wherein energization of a coil causes the armature of the device to transfer from one position to another, and energization of another coil causes the armature to transfer back' to its original position.

Another object is to provide'a magnetic latching device wherein transfer of the armatureis effected by re ducingthe flux in a magnetic holding circuit, and wherein the electrical circuit for producinga nullifying flux is automatically disconnected upon transfer of the relay armature. v

' It is a further object to provide amagnetic latching device that will hold the armature and prevent a change in the position of the contacts when the control voltage is removed, andwherein it is impossible to simultaneous ly close the contact circuits in more than one position, i.e., either the trip or close position under any condi- ,tion of mechanical or electrical failure.

It is also an object of this invention to provide a magnetic latching device wherein the coils are energized independently and which is operable on either direct current or alternating current up to at least 400 cycles per second. It is a further object of this invention to provide a magnetic latching device which is operable by alternating current ofa frequency of at least 400 cycles per second with- .out the necessity forrectifying such alternating current. Itis yet anothergobj ect of this invention toprovide a devicehaving an armaturemovable by alternating current, that avoids the problems of eddy-current losses, and

a eme- I I r I It is an additionalobject of this invention to provide ;a relay operable without a returnspring.

does not require'expensive, heavy and complex laminated is a still further object of this invention to provide I on the lower ends of terminals 3 and pivotally mounted adjacent the end of the common cen 'ter leg and alternately pivotal into contact with the other leg of each of the U-shaped members.

These and other objects and advantages of the present invention will become more apparent when read in the light of the accompanying drawings and specification, wherein: l

FIG. 1 is a sectional view of a preferred embodiment of the invention with the armature in one of its alternate positions. FIG. 2 is a sectional view taken in the plane of line 2-2 in FIG. 1 illustrating the manner of contacting the primary terminal contacts as well as auxiliary terminal contacts.

FIG. 3 is a diagrammatic view of the device of the present invention showing the device latched in one position and the flux circuit for accomplishing such latching.

FIG. 4 is a diagrammatic view of the device of this invention showing it latched in the alternate position by the other flux circuit.

FIG. 5 is a schematic view of the device showing the manner of interconnection of the operating coils and their associated contacts.

FIG. 6 is a schematic view of the concept of this invention applied to a relay.

Referring to the drawings, wherein like reference numerals have been used throughout the several views to designate like parts, and with reference first to FIG. 1, the device of this invention is shown by way of example as used for actuating a double throw magnetically latched contactor 1 which may be either normally open or normally closed. Contactor 1 includes a housing 2 of a magnetically shielding material of low permeability. One or more each of terminals 3 and 4 extend outwardly from housing 2. As shown in FIGS. 1 and 2, the in vention is illustrated in the form of a three pole double throw contactor; however, as will be self-evident to those skilled in the art, my invention is not limited to use with any particular number of poles. A terminal pair is formed with each of poles 3 and 4 and its common center terminal 5. Each of the terminals has a terminal seat 6 resting on a terminal support 7, preferably formed of hard rubber or a similar material, and is insulated from housing 2 by a bushing 8 of suitable insulating material.

A conventional spring blade type contact arm 9 is secured conductively at its midpoint to the inner end of each center terminal 5. The ends of contact arm 9 extend outwardly into proximity with the terminals 3 and 4 and have contacts 10 and 11 thereon for electrically engaging contact arms 12 and 13 on the lower ends of terminals 3 and 4, respectively.

A magnetic latching unit 14 is provided for actuating contact arm 9 to alternately close and open the contacts 4. The latching umt 15 supported within housing 2 by a mounting plate 16 of a suitable non-magnetic material attached to the under- .side of the housing cover 17 Latch 14 includes two symmetrical U-shaped permeable segments having a common center leg. The lefthand portion, as shown in FIG. 1, includes a permeable a cylindrical configuration as shown herein, it is not limited to any particular shape. Armature 22 is pivotally mounted by transverse pin 23 so that it is adjacent to the pole face 24 of a common central core element 25. As a result, only a very small air gap exists therebetween,

path of low reluctance. .U-shaped permeable flux path is provided by core 30,

. 13 are brought into engagement.

27 integrally attached to the lower end of core 19 and extending normally therefrom toward center core 25. At the inner end of member 26, leg 28 extends upwardly in a spaced parallel relationship with the center core. A

permanent magnet 29 is positioned within this space between leg 28 and core 25, with its south pole adjacent the center core and its north pole adjacent the inner surface of leg 28. Thus, core 19, L-shaped core 26, magnet 29 and common core 25 form a U-shaped permeable flux A similar matching right-hand L-shaped core 31, permanent magnet 32 and common center core 25. The flux paths across the open ends of the permeable U shape d arrangements are completed by centrally, pivoted armature 22. The armature is of a very shallow V-shapcd configuration so that when one end thereof is adjacent to or in contact with the pole face of either core 19- or core 30, the opposite end of the armaated end portions of contact arm 9. When the right-hand end of the armature is in a raised position and displaced upwardly away from its complementary upper pole face on core 30, projection 37 contacts the arm 9 to raise it and hold contacts 11 away from contacts 13. The other projection 36 then is in its lowered position so that contacts and 12 are in a closed, current-carrying relationship. Reversal of the armatures position causes projection 36 to open contacts 10 and 12, while contacts 11 and Coils 3.8 and 39 circumscribe cores 19 and 30, respectively, and provide the means for alternately and individuallyunlatching the device to close or open the respective circuits controlled thereby.

As illustrated diagrammatically in FIG. 3, no current is flowing through either of the coils, and end 33 of armature 22 is at rest adjacent pole face 20. In this position of the armature an air gap is formed between end 34 of the armature and pole face 35 of core 30. The flux field of the permanent magnet 29 is that indicated by arrows A, passing through the relatively low reluctance path provided by member 26, core 19, armature 22 and center core 25, This causes. north and south poles to .exist at the pole face 20 and armature end 33, respectively, so that an attractive forceresults and the plunger is held in the position shown. 7

. The flux circuit B of magnet 32, which includes core members 30 and 31, and center core 25, also exerts a V forceon the armature. However, the relatively large air gap between armature end 34 and pole face 35 of core 30 provides such a high reluctance drop compared with that of flux circuit A that for all practical purposes the flux flowingthrough circuit'B is so insignificant that it may be neglected when the armature is in the position of FIG.

" 3 and no current flows through the coils.

In order to change the position of the armature 22, coil 38 is energized by current-of an intensity and polarity to provide a magnetomotive force opposing and substantially neutralizing flux field A of permanent magnet 29., flux field A is reduced in strength, the attractive forcebetween pole face 20 and armature end 33 is proportionally weak- Yen'ed and ultimately becomes less than the relatively small attractive force existing between the separatednorth and south poles at pole face 35 and armature end 34. When this'occurs, armature end 34 is" pulled toward pole face 35 where the larger force then exists. As'the armature ture is spatially displaced from the pole face of the other core, thereby creating a high reluctance air gap in the other magnetic circuit path. This is shown in FIG. 1

moves, its velocity accelerates because the closer the armature end approaches the pole face the greater becomes the attractive force therebetween. Thus the armature is caused to pivot to the positionv of FIG. 4, moving armature end 33 away from pole face 20. This allows contacts 11 and 13 to come into operative engagement, while it raises contacts 10 out of engagement with terminal contacts 12. This action closes the load circuit connected to any terminal pair 4 and 5, and opens the load circuit connected to any terminal pair 3 and 5.

It should be borne in mind that this transfer of the armature resulted directly from the force, exerted by a permanent magnet, and not from a force from a coil. The flux of the coil served only to neutralize the pull of one permanent magnet, to allow a second permanent magnet to pivot the armature.

With the armature now transferred tothe position shown in FIG. 4 and as described above, it is retained by the flux field B of the permanent magnet 32 whichnow passes through a field of =low reluctance. The armature is held in this position until coil 39 is energized with proper polarity to introduce a magnetomotive force neutralizing the flux in circuit B. The armature then moves back to its initial position with armature end 33 attracted to and in contact with pole face 20. In this position con tacts 10 and 12 are engaged and contacts 11 and 13 are disengaged whereby the load circuit connected to any terminal pair 3 and 5 is closed and any load circuit connected to terminal pair 4 and 5 is interrupted.

current circuits may be used for controlling the latch without any necessity for lamination of the magnetic core I elements of the device, since it will operate on a single such pulse of proper polarity, and the transfer force on The weight, complexity and cost of the unit are substantially reduced by this improved arrangement, with eddy-current losses being-obviated even though the device operates on alternating current.

In this respect it may be con that half cycle of alternating current having the proper 'polarity to openthe switch is effective therefor. 50

As shown in FIG. 2, pairs of auxiliary contacts 40 may be actuatedby knife blades 41 depending from armature V 22 in' a manner similar to the actuation of contact pairs 10, 12 and 11, 13 to close or interrupt auxiliary control or svw'tching circuits connected to auxiliary terminals 42.

A coil circuit arranged so that the movement of the armature automatically disconnects the control signal input circuit, is shown in FIG. 5. Coil 38 is electrically energized by means of a signal input connection 43. *The other end of coil 38 is electrically connected to contact 12, and when movable contact '10 is in engagement with contact 12, the circuit is completed to center terminal 5.

Thus, application of current to coil 38 to cause the armature to move clockwise under the attractive force of magnet 32, opens contacts 10 and 12, which interrupts the control circuit to coil 38. Magnet 29 then is no longer neutralized, butthe armature will be retained in its new position by magnet 32. This shifting of the armature Y closes contacts 11 and "13, which completes the circuit for the other coil 39. 'Iherefore, a similar action takes 7 place upon application of a control pulse through con-v ductor 44 to coil 39, with the armature moving counterclockwise toopen contacts 11;and 13and' interrupt the control circuit existing between conductors 5 and 44.

This arrangement assures thatthe device will not oscillate, despite the fact that it operates on a very short pulse.

No rectifiers are required for A.C. operation of the device. sidered to be analagous to a diode rectifier, since only A modified form of thisinyention may be seen in FIG. 6as applied to a relay type device. Here a permanent magnet 46, is positioned with its south pole in contact with one leg 47 of a U-shaped permeable core member 48, and itsnorth polein contact with a toreshortened leg 49 of another U-shaped permeable core member 50. A pivoted permeable armature 51, completes magnetic circuits through either U-shaped-core when the adjacent end of the armature is in contact with po le face 4-or 55. By this construction it will be noted that the flux field C of permanent magnet, 46 passes only through member 50 and the leg 47 ofrcore member 48 which is'located adjacent the magnet. A coil 57 is positioned on leg 58 ofcore 50. An additional coil59 is located on leg 60 of core 48. Coil 57 serves the purpose of introducing a magnetomotive force in core 50 toreduce the flux of the permanent magnet, While coil 59 is a pull coil in a typical relay type circuit. Preferably, coils '57 and 59 are connected in series and wound in a manner such that energiZation of the circuit causes the magnetic flux to be neutralized in core 50, while, at the same time, a magnetomotive force is induced in core 48to attract the end of the armature 51 against pole face 54. Upon vdeenergization of the circuit, flux field C again asserts itself to at- .tract the armature end to pole face 55.. o

This means that relay actionis provided without the use ofa return spring; As a result, it is notnecessary for large spring forces to'be' overcome in moving the armature. Also, difiiculties-frorn vibrations imposed on the pairs in a load circuit.

The foregoing detailed description is to be clearly understood as given byway of illustration and-example only, the spirit and scope of this invention being limited solely by the appended claims.

1. A latching device comprising a magnetically operable pivotal member alternately movable between a first and a second position; a first fixed magnet having a magnetic flux field; a first magnetic circuit for the flux of said first magnet; a first means for producing a flux in said first circuit in opposition to the flux of said first magnet; a second fixed magnet having a magnetic flux field; a second magnetic circuit for the flux of said second magnet; and .a second means for producing a flux in said second circuit'inopposition to the flux of said second magnet, saidfirst and said second means for producing a flux beingselectively and independently operable, said pivotal member having portions forming portions of said first and second magnetic circuits "for movement by the fixed magnet in either one of'said circuits when the flux of the fixed magnet in the other of said circuits is opposed by the means for producing flux in such o'ther circuit. I

2. A magnetically latched contactor comprising a pivotal member alternately movable between a first and a second position; a plurality of fixed contact elements; a contact on each arm of said pivotal member, the contact on one arm of said pivotal member being placed in electrical contact with one of said fixed contact elements in said first position, and the contact on the other arm of said pivotal member being placed in electrical contact with another of said fixed contact elements in said second position; a first relatively fixed magnet having a magnetic flux field; a first magnetic circuit for the flux of said first magnet, said first magnetic circuit including an arm of said pivotal member and arranged to conduct said flux therethrough in one direction thereby to urge the contact on said one 'arm of said pivotal member into contact yvith said one fixed contact element; means for producing a flux in saidfirst circuit in opposition to the flux of said first magnet; a second relatively fixed magnet; 'a second magnetic circuit for the fiux of said second magnet, said second magnetic circuit including another arm of said pivotal'member arrangedto conduct the flux of said second magnet -therethrough in an opposite direction thereby to urge the contact on said other'arm of said pivotal member into contact with said other of said fixed contact elements; and means for producing a flux in said second circuit in opposition to the flux of said second magnet, said first and said second means for producing a flux being selectively and independently operable.

3. A magnetic latching device comprising a first mag net having a magnetic flux field; a first magnetic circuit for the flux of said first magnet; a second magnet having a magnetic flux field; a second magnetic circuit for the .flux of said magnet; a pivotal armature member forming part of said first and second magnetic circuits and pivotal between a first and a second position; contact elements ,on adjacent fixed st-ructure; contacts on said armature adapted to alternately contact said fixed contact elements for alternately closing and opening electrical circuits; and means for independently and alternately producing a flux field in said first and second magnetic circuits for opposing and substantially neutralizing the flux fields of said .first and second magnets whereby said pivotable armature member maybe alternated between said first and second positions by the magnet whose flux field is unopposed. v v

I 4. A magnetically latching contactor comprising 1 a pivotal armature alternately movable between a first position and a second position; contact elements on adjacent fixed structure; a contact on each arm of saidpivotal armature, a contact on one of the armature arms being placed in contact with one of said fixed contact elements in said first position of the armature, and the contact on the other arm of said armature being placed in contact with another of said fixed contact elements in said second position; a first magnet; a first magnetic circuit for the flux of said first magnet; a first means for producing a fiux in said first magnetic circuit in opposition to the flux of said first magnet, said first flux producing means-being electrically connected in series with one of said fixed contacts in a manner whereby momentary energization of said first flux-producing means causes said pivotable member to move to its second position by the flux of said second magnet and the adjacent contact onsaid armature'to open from said one fixed contact thereby automatically disconnecting said first flux-producing means; a second magnet; a second magnetic circuit for the flux of said second magnet; and a second meansfor producing a flux in said second circuit in opposition to the flux of said second magnet, said second flux-producing means being elecmove to itsfirst position by the flux of said first magnet and said the adjacent contact on said armature to open -fr0rn said other fixed contact thereby automatically disconnecting said second flux-producing means.

5. A magnetic latching device comprising a first substantially U-shaped magnetically permeable core member including a permanent magnet therein; a second substantially U-shaped magnetically permeable core member including a second permanent magnet therein; said first and second substantially U-shaped members having a common leg; a first electromagnetic coil means for producing a flux in said first substantially U-shaped member in opposition to the flux of said first permanent magnet; a second electromagnetic coil means for producing a flux in the second of said substantially U-shaped core members in opposition to the flux of said second permanent magnet; and a pivotal armature having a central portion at its pivotal axis in proximity to the end of said commonleg and its outer ends movable into and away a from contact wth the separatelegs of said first and second substantially 'urshaped members, said first and said second electromagnetic coil means "being independently and selectively operable.

6. A magnetic latching device comprising a first elongated core element; anarmature, said armature being disposed with its central portion adjacent one end or said first core element and being pivotal about said central portion; a first permanent magnet one side of which is adjacent and in flux-conductive relationship with one side of said elongated core element; a second core element on the opposite side of said first permanent magnet and in flux-conductive relationship therewith, said second core element extending to a position adjacent 'one end of said armature; a second permanent magnet one side of which 'is adjacent and in flux-conductive relationship with the opposite sideof said first core element; a third core ele- V ment adjacent and in flux-conductive relationship with the opposite side of said second permanent magnet, said third 'core element extending to a position adjacent the opposite end of said armature, whereby said first core element said second core element and one end portion "of said armature form a magnetic circuit for saidfirst permanent magnet, and said first core element said third 1 core element and the opposite end portion of said armature provide a magnetic flux circuit for said second permanent'magnet, said armature being pivotal from and to a position in which said first end portion thereof is adjacent said end of said second core element and offers a low reluctance to thefiux in said first magnetic circuit and said second end portion is remote from said end of said second core element and offers a high'reluctance to the flux in said second magnetic circuit, and a position in which said second end portion of said armature is adjacent said end of said third core element and offers a low reluctance to the flux in said magnetic circuit and said first end portion is remote from said end of said second core element and ofiers a high reluctance-to the flux in saidfirst magnetic circuit; a first electromagnetic coil means in said first magnetic circuit and energizable to providea flux opposite and substantially equal to the flux of said first permanent magnet in said first magnetic circuit; a second electromagnetic coil means in said second magnetic circuit, said second electromagnetic coil means being energizable to provide a flux opposing and substantially equal to said flux of said second permanent magnet, said electromagnetic coil means being independently and selectively operable.

7. A magnetic latching device comprising a pivotal armature, a duality of permanent magnets, a flux circuit for each of said permanent magnets, the flux circuit for one of said magnets including one end portion of said armature, the flux circuit for the other of said permanent magnet including the other end portion of said armature,

said flux circuits including a common permeable element interposed between said permanent magnets, said armature being pivotal between two positions mom of which said armature provides a relatively low reluctance to the "flux of the magnetic circuit for said one permanent mag;

net and a relatively high reluctance to the flux of said other magnetic circuit, and in the other position of which said armature offers a relatively low reluctance'to the flux of said other magnetic circuit and a relativelyhigh reluctance to the flux of said one magnetic circuit, {an electromagnetic coil means in either of-*said magnetic circuits, and means for independently and alternately energizing said coil means for producing a fiux in either of a said circuitsopposite'to and substantially neutralizing circuit. 1 V

8. A device as recited in claim 7 in which said means for energizing said coils includes a source of alternating current. i I I v v 9. A magnetic latching device comprising an annature; means for pivotally mounting said annatunete duality of magnetic circuits, the first of said circuitsincludinga first permeable member adjacent said arm-ature on one side of said pivotal mounting and including portions of said armature on said oneside't-hereof, the second of said circuits including a :second'permea-ble member adjacent said armature on the other side of said pivotal mounting and inciudingportions of said armature on said other side'thereof, said armature being pivotal between a first position in which said armature on said one side is closer to said first permeable member than the distance between said armature on said other side'and said second permeable member for providing a-rel'atively low reluctance in said first circuitand a .relativelyhigh reluctance in said second circuit, and a second position" in which said armature on said other side is closer to said second permeable member than the distance between said armature on said one side and said first permeable member for providing a 're-latively'low reluctance in said second circuit and a relatively high reluctance in said first circuit; a first permanent magnet means in said first circuit for providing a flux field therein attracting said one side of said armature to said first permeable member; a

second permanent magnet means in said second circuit for providing a flux field therein, attracting said other side of said armature to said second permeable member, a first electromagnetic coil means in said first circuit for producing a fiux field substantially neutralizing the flux of said firstpermanent magnet means, and a second electromagnetic coil means in said second circuit for providing a flux field substantially neutralizing the flux of said second permanent magnet means, said coil means being independently and alternately operable.

References Cited in the file of this patent Fischer et al. June 14,

the flux therein from the permanent magnet of such 

